Caffeine Prolongs Exercise Duration in Heart Failure

BackgroundCaffeine increases submaximal exercise performance in healthy young subjects; its effects on exercise tolerance in heart failure (HF) have not been characterized.Methods and ResultsTo determine whether caffeine increases exercise tolerance in HF, caffeine (4 mg/kg intravenously, equivalent to 2 cups of coffee) or vehicle were infused into 10 treated HF patients (left ventricular ejection fraction 25 ± 2 %), and 10 age-matched normal subjects (N) on 2 separate days in a double-blind, randomized, crossover design. We measured heart rate, blood pressure, and ventilation at rest and during graded cycling (15 W/minute) to peak effort. Peak oxygen consumption was unaffected in either group. Mean exercise time was unchanged in N (1013 ± 87 versus 988 ± 107 seconds; P = .86) but was significantly increased by caffeine in HF (from 511 ± 28 to 560 ± 37 seconds; P = .004) despite an increase in peak minute ventilation (P < .05). Resting and peak blood pressures were higher after caffeine (P < .05) in HF, not N.ConclusionCaffeine allows HF patients to exercise longer at peak effort.